It is known to make pressure sensors by micromachining silicon wafers to form a diaphragm and a responsive element. U.S. Pat. No. 4,930,042, for example, illustrates a pressure sensor having an electrical readout in which the capacitance of the sensing volume is measured as a function of pressure.
It is also known to fabricate a vibrating, optically driven element from highly doped silicon, using the doping as an etch stop, such as the technique disclosed in "Novel Optically Excited Resonant Pressure Sensor", Electronics Letters, May 12, 1988 Vol. 24, No. 10, page 573, but such devices have a significant temperature dependence caused by the dissimilar doping that presents great difficulty when they are used over a broad temperature range.
The art has sought a pressure sensor that is capable of operating at high and low temperature extremes and therefore is insensitive to temperature variations. There is a problem in that the element of the diaphragm which is sensitive to the pressure will usually have also a temperature dependence. Further, the use of dissimilar materials within the device will inherently exert a strain based on differential thermal expansion that is confused with the variations due to pressure.
The art has long sought a rugged pressure sensor capable of operating at high and low temperatures and having a reduced sensitivity to temperature variations.